This invention relates to a transmission announcement system for use in conjunction with a data broadcast system in which data is served from content servers over a unidirectional broadcast network to multiple clients. The transmission announcement system enables the servers to send out announcements for upcoming broadcast transmissions to the clients. These announcements may be sent over the broadcast network, or they may be sent over a secondary link independent of the broadcast network. The announcements contain sufficient information to prepare the clients to receive the broadcast transmissions.
Conventional computer networks are bi-directional, allowing data communication in both directions between the servers and the clients. Transmitting data over these bi-directional data networks has been a mainstay of computer technology for many years and the communication protocols are well established. Under conventional communication protocols, it is common for the client to initiate connection with the server and to request desired data from the server. As part of the request, the client sends information pertaining to how the data should be sent.
Apart from the classic bi-directional data networks, there is an increasing interest in the use of broadcast networks to deliver computer data and other content to clients, akin to the broadcast delivery of television or radio. Broadcast networks are unidirectional in that data flows from the server to the clients, but no return communication is possible over the same communication path. More particularly, broadcast networks are often characterized as a shared highly asymmetrical network resource with a limited, if not completely absent, low speed return path that does not need to be active to receive transmissions. As a result, the common protocols used for two-way communication over a bidirectional network, such as client-driven connections and data requests, cannot be supported by the broadcast network because the clients are unable to communicate over the broadcast communication link to the server.
The inventors have developed a system and method which address this problem.
A transmission announcement system facilitates broadcast data transmissions over a unidirectional broadcast network by utilizing pre-broadcast announcements which inform clients of upcoming data transmissions prior to their broadcast and instruct the clients of how to receive the broadcast transmissions.
According to an aspect of the invention, announcement servers (which may or may not be the same as the content servers that serve the data for the broadcast transmissions) generate announcements containing information specifying how associated upcoming transmissions are to be delivered over the broadcast network. The announcements might correspond to single transmissions, or might provide a list of transmissions. The announcements contain such information as a broadcast locator (e.g., a universal resource locater (URL) on the Web, a broadcast channel, etc.), an identity of the content server that will be serving the data for the transmission, a time of transmission, a broadcast protocol, a subject matter of the data transmission, a length of the transmission, and a rating of the content contained in the transmission.
The announcement server makes the announcements available to the clients over the broadcast network on a reserved multicast address or over a secondary link other than the broadcast network. As one example of the secondary link, the announcement servers might send the announcements to a multicast address over a public network, such as the Internet. As another example, the announcement servers might post the announcements at a publicly accessible site on the network, such as at a Web site on the Internet. The clients receive the announcements via the secondary link by, for example, monitoring the multicast address or occasionally accessing the Web site.
According to another aspect of the invention, a client filters the announcements according to predetermined criteria, keeping the announcements satisfying the criteria and discarding the rest. Filters used by the client can be filters automatically created in software based upon user behavior patterns, or userdefined custom filters created from parameters entered by a user. For the announcements that are kept as being of interest, the client searches them to extract the broadcast protocol, broadcast locator, transmission time, and any other information pertaining to retrieval of the broadcast transmission. The client tunes a broadcast receiver to the broadcast locator and launches a receiving application to receive the transmission according to the broadcast protocol.